We report a novel fabrication process of a mesoporous Si3N4 membrane on an Al2O3 support via a non-aqueous sol-gel technique. The membrane was prepared by dipping an alpha-Al2O3 Support disk into a silicon diimide sol that was synthesized by catalytic ammonolysis of tris(dimethylamino)silylamine, H2NSi(NMe2)(3). The SEM image and nitrogen adsorption analysis indicate that amorphous Si3N4 layers with nano-sized pores have formed on the surface and also inside the pores of the Al2O3 support disk. The new membrane demonstrates high selective absorption of NO2, suggesting a potential application as a selective filter for gas sensors. (c) 2006 Elsevier B.V. All rights reserved.